Load limiter for speed governors



Feb. 9, 1954 |l H, SWEET 2,668,519

LOAD LIMITER FOR SPEED GOVERNORS Filed Oct. 29, 1952 CONSTANT PRESSURE l 6V H FLUID WRC( 4- FUEL 0N G INVENTOR.

Patented Feb. 9, 1954 UNITED STATES PATENT OFFICE.

LOAD LIMITEE FOR SPEED' GOVERNORS Floyd H. Sweet', Euclid, Ohio, assignor toy The. MarquetteMetal Products Company, Cleveland Ohio,a corporation of Ohio Application October'29, 1952', Serial.' No. $137,543

7v Claims. l

The invention relates to improvements in load or torque. limiters for engines controlled' by governors. The objects include provisiony of animproved: hydraulic relay governor load limiter which operates as' a combined. function of load asfrepresentedby the-position. of a fuel regulatelement: of the governor and of actual engine speed; and toa centrifugally acting load limiting mechanism of a governor requiring very small space and yweight mass, yet which is highly sensitive to enginespeed changes requiring itsoperation. and is. otherwise eicient and freefrom hunting. or cycling during its action to!y limit load or torque.. Other objects include various specific' improvements in governor load limiting as: will appear from the following description ofa preferred embodiment,

In the drawing, Fig. 1 is a schematic view of a vtypical hydraulic. relay .governor incorporating the invention; Fig. 2 is a fragmentary longitudinaljvertical sectional full scale View of a speed measuring and connected fluid valving hydraulic mechanism forming part of an actual physical embodiment. v

AThe main governor unit, as shown in Fig. 1 (representing a typical hydraulic relay speed governor mechanism), has a casing A, containing an engine-speed-change-detector, including flyballs B; a Speeder spring C and a pilot valve the movablev part of which is plunger D (sometimes hereinafter referred to as the governor pilot valve). The pilot valve controls the operating efliect of substantially constant pressure iuid (governor oil` as from a pump and accumulator, not shown, admitted by line or passage F) on a servomotor, represented by power piston H. Passage F is continually connected to the lei-t hand end of the servomotor; Passages G and G' between the pilot valve and the right hand end of the servomotor are normally interconnected. Governor oil, in the illustrated equilibrium or steady-state positionof the pilot valve is trapped by that valve in lines G and G in contact with relatively larger area (tace J) of the' power piston H. whose smaller area (face I), as indicated above. is continually subjected to governor oil pressure through line F. Line E' has a. branch F" which is. normally closed.

To cause. fuel-on (leftward) movement of the power piston H. the pilot valve plunger (by lowering as in. response to diminished engine speed,1 thus opening porty E) admits governor oil through. G, G tothe right hand cylinder chamberlof the power'piston; and, to cause fuel-oir or reverse .piston movements, the. pilq valve plunger israised and then. spills trapped oil at pilot valve. sump connection port S.

A hydraulically acting feedback (temporary speedv droopor compensation.)A system between thel governor power pistonv I-I and its piloty valve D is diagrammatically represented as comprisingl an. actuating displacementv pump N; oil. passage O; receiving piston P which is spring-connected., to.. the pilot valve, and a needle valve R for adjusting leako. The system. is7 substantially that. of A. Kalin Patent. 2,219,229., dated October 22, 1940.

The governor, as shown,. has a known type of speed settingl mechanism including a lever. I0 suitably connected between itsends tothe Speeder spring C. End portion Ilia. or the lever is. subject. to. speedsetting operation (vertical'movement). as by a hand. knob or suitable power means not shown.. End. portion lob is: connected for similar movementV by a speed droop4 linkage, forming noessential part of the present invention but which, as partially shown, includes a bell crank Il supported on a fixed pivot t2, one arm of the bell crank being connected to lever It) and the other, at vertically adjustable pin` I3 on said other arm, being connected to a powerpiston follower lever l5 for movement by that lever through its-connection with the power piston at le. In the illustrated position of pin I3 that. pin is concentric with a fixedpivot (not shown) of the follower lever on the governor case. The linkagewhich is accordingA to A. Kalin. Patent 2,341,384, is thus shown as set for Zero. speed droop..

In the type of the Marquette Metal Products Company governor, essentially as shown in the last above mentioned patent, the. power piston follower lever l5 is so located as. to form a convenient means for operatingv a load limiting valve T 'thereof (shown at the far right in Fig. l) partly as a function of power piston movement in the fuel-on" direction thereof, Fig.. l.

A plunger 2i? of valve T controls ports 2| in sleeve 22 (which ports, as shown, are connected to trapped fluid line G) to close line G when plunger 25) is depressed a predetermined distance. At nearly the same time as ports 2| are closed by downward movement of valve plunger `2() a lower land of the plunger opens line portion G. at sleeve ports 23, to commence spi-lling the duid trapped in Contact with larger piston face J througha sump-connected passage S".

Valve. plunger loof valve 'IT-is'arrangedfor operation byv a. oating lever 2.5 having a variable fulcrum y26: (on a stem portion of a servomotor piston 28, to be described presently); and the leftward end of lever 25 is connected for movement by the power piston follower lever l through a rack and cam mechanism U. Servo piston 28 is caused to operate as a function of engine speed through a pilot valve plunger 28 as will be described later.

Mechanism U comprises, as shown in Fig. 1, a slidably mounted toothed rack 38 biased to the right against a stop 30 by a relatively strong spring 3l; an operating abutment finger 32 on the follower lever which engages a pin 33 on the rack; an angularly movable cam 35, and a pinion 38 normally rigid with the cam and having its teeth in constant mesh with those of the rack 38. A slot 38 in the cam embraces a pin 38 projecting from the floating lever 25; and the cam slot is so designed that, after fuel-on movement of the power piston H through its no-load or normal idling range (from no-fuel position to midposition, for example, as would be determined generally by proper adjustment of abutment finger 32, shown as locked in place on lever l5 by cap screw 32', Fig. 1) the pin 33 of the rack is engaged by abutment nger 32, and then each unit increment of power piston travel in the fuel-on direction operates to raise the left hand end of the floating lever by a proportional unit incre-ment. That, as will be apparent, can tilt the lever about its fulcrum 26 to depress the valve plunger to close load limit valve ports 2l and open spill ports 23.

Whether or not the load limiting valve action just above outlined occurs is contingent upon actual engine speed as measured by auxiliary flyball and connected servo piston valve mechanism V, which mechanism determines the position of floating lever fulcrum 2G on servo piston 28. Mechanism V is capable of preventing load limiting action of valve T from taking place whenever the engine speed is suiiiciently high to enable safe or desirable increase of fuel to the engine.

Engine speed measuring (etc.) mechanism V, as shown best in Fig. 2, includes yball assembly 5 on a rotary ballhead 6 which is continually connected in a suitable manner for rotation by the governor drive shaft (not shown). The flyballs 'l and their centrifugal-force-opposing or loading spring 8 are designed so that the ilyballs assume a different position for each engine speed above the maximum .no-load speed, i. e. idling speed or through any other desired speed range. The flyball reactance force of spring 8 is adjustable by means of a threaded cap 8 in a spring-housing sleeve portion 48 of the ballhead 6. The spring 8 is maintained under predetermined axial strain between the cap 8 and a thrust plate 4| which is threaded to a push rod 42 freely slidable in the ballhead.

The pushrod 42 of the auxiliary flyball mechanism V, for initiating downward pressure-actuated movement of the servo piston 28, acts directly against a head portion 28' of servo piston pilot valve plunger 28, beneath which head portion a light spring 44 biases said pilot valve plunger upwardly, e. g. returns the plunger toward the ballhead assembly, as when the reactance force of spring 8 is overcome by centrifugal force acting on the auxiliary llyballs.

Mechanism V is enabled to have a very small flyball mass and, in general, be of compact design through use of servo piston 28 and small diameter, freely movable pilot valve thereof. The

effective opposing forces of springs 8 and 44 Qn pilot valve plunger 28 cause the necessary movement of that plunger and the latter valves operating fluid to move the servo piston, thus to shift the floating lever fulcrum 26 as a function of engine speed. The pilot valve plunger 28 is always exposed to negligible pressure at both ends (bottom end through sump-connected passage S) and the servo piston mechanism is designed for fluid pressure operation essentially as is the governor power piston H, through governor fluid supply at F' under servo piston pilot valve control at ports 5I and 52. Trapped oil in space 54 above the servo piston proper is spilled at ports 5I by. upward pilot valve plunger movement to cause upward piston travel due to pressure in lower piston cylinder space 55, and governor oil is admitted to space 54, to cause lowering of the piston, by downward movement of the valve such as will open ports 52. Thus the piston 28 is power-operated and caused to follow all pilot valve movements, and the resistance to movement of the pilot valve plunger 28 is only that of friction between it and its small bore.

The engine speed measuring flyball mechanism 5 can, if desired, be rendered ineffectual, without interfering with the operation of the main governor in controlling the engine, by removing the cap 8 and spring 8 from housing 40 and then-with one yball 1 suitably held in its maximum outward position as against the stop provided by the lower end of housing 40-replacing the cap without the spring in a screwed in position of the cap such that its stem portion 43 abuts the top end of pushrod 42. The relatively weak return spring 44, acting through the head plate 28 of pilot valve 28 on the pushrod. then holds the flyballs in their outwardmost positions; and, by reason of the continually elevated pilot valve and consequent fluid pressure follow-up action on its servo piston, the fulcrum 28 of lever 25 holds the valve plunger of mechanism T out of range of its `controlled ports. The point in the travel of fuel-metering servomotor piston H in the fuel-on direction at which valve plunger 28 of valve T interrupts further fuel-on movement at a predetermined engine speed is precisely adjusted to meet engine and load requirements as a final operation after installation of the governor on the engine. To render the precision adjustment means readily accessible through the top of the governor case (assuming the usual cover partly suggested at A', Fig. 1, is not yet in place) said means is arranged to function by varying the port-controlling rela-- tive position of the plunger 28 and sleeve 22 of valve T. As illustrated the sleeve 22 is screw threaded at 22' into the governor case A. the sleeve has gear teeth at B2, and a suitably supported upright shaft 68, manipulable as by a screw driver or other tool, has teeth 6I in con.- stant mesh with those of the valve sleeve. Shaft 68 has a locking spring 63 to maintain the final adjustment. The minimum engine speed at which a particular load can be imposed upon the engine is separately adjustable through the top of the governor `case by turning the cap 8 in ballhead mechanism 5 to vary the acting force of the ilyball loading spring 8. The cap is also provided with suitable adjustment maintaining means, not shown, preferably a lock wire.

In operation, as soon as the power piston H has been moved by hydraulic relay governor action in the fuel-on direction into its preadjusted load carrying range, furtherpower piston movement. in that direction tends, through cam 5 mechanism! U", l-todepress `plrmger 29',A of v valve-11:1; closing ports "Zi 'andl arresting-further power piston movement inf tliatfdirectien; but, solong as the actual enginespeedL isapprcpriat'eTA te load, auxiliary iiyball's of mechanism V maintain such positioning of iicati'ng.- leverl pivot TZYe that theservomotor-iinpartedi canr a'ction'- or? mechainis'm Uf is ineffective'. YThed'esi'gI-r vandadjustment-of the mechanism-vas a whole-lis such that Supply'of operating' fluidi to the-governorservomotor throughline Cri becomes-blecked at" ports 2i? of valve T` when the' maximum lead' is imposedy at a predetermined? speed?,`v thusfprev'enting applicationl oiiradditi'onal loading-r at thats-need'.

The following features of the present governor load limiter construction co-operate in preventing hunting such as.- is aptto occur withv a centrifugally acting. load. limiter of the general type shown:

1. "Ihe"v servo piston pilotv valve plunger 259 re- 'iuiixes alniostY negligibleVA operating force; hence thepositibnY of-deati-ng leveriiullcrum 2f5`is= always truly representative of existing engine speed (negligible lag).

2. Spilling of operating fluid from the governor servomotor necessarily results in a gradual movement of the power piston toward no-fuel position because, as the decelerating flyballs l commence to cause opening of spill ports 23, the thus initiated "fuel-oif movement of the power piston tends to close them (essentially the same feedback action as the servo piston 28 has).

3. Servomechanism-actuated cam 35 of mechanism U acts positively in two directions on the floating lever 25 with negligible backlash, to that any reversal of governor power piston movement direction is immediately translated into repositioning .of the plunger of valve T. Spring 3| of rack 30 is strong enough always to insure rightward movement of the rack and counterclockwise movement of the cam 35.

Referring to the portion 38' of the slot of cam 35 which is concentric with the mounting axis of the cam, the cam is so adjusted on its supporting shaft that the follower pin 39 on the iloating lever 25 encounters the concentric portion slightly before the power piston I-I, in its fuel-on movement, has arrived at the proper full load position. is operating at rated load and speed, the main governor Speeder and pilot valve mechanisms are in full control, and a certain range of servomotor movement necessary for maintenance of set speed despite minor torque variations is perr mitted without interference by the load limiting mechanism hereof.

I claim:

1. In a hydraulic relay speed governor for engines, the governor having speed setting means acting through speed-change-responsive pilot valve means to cause engine-fuel-regulating movement of a servomotor, a load limiting Valve between the pilot valve and a pressure chamber of the servomotor, which chamber receives fluid under control of the pilot valve to cause fuelon movement of the servomotor, the load limiting valve including a port-closing and portopening member operable to block flow of fluid to said chamber and to spill fluid from said chamber, a iloating lever connected to said member to move it to said port-closing and portopening positions, servomotor-connected means including a variable-fulcrum-establishing means for the lever for enabling such movement of the Thereby, when the engine l'everf'byf thefservomoter, an klengine@'speediarreasfnir'ig'4 meansf connected? for'cpt-.mation .by the fengine through the governor and having an output element' inithefornr of a valve plunger',4 a; Aservo 'piston having duid pertsffcontr-.olled solely by movement" of theV valvel plunger in opposite di'- recticn's` toz cause the pistoni to follow all move:- 'ments of the valve: plungen. and. another' variable fulcr'um for the. lever' operatingly' connected` for movein'entof the lever lby the. lservo:pist'en in the' same pla-neas the leverI is moved` by the servomotor-connectedmeans, whereby load limiting operation, on: the servomotor'by the loadl limiting valve.A is a combined function of servo'- motorpesitionand-enginespeed.`

2".Ihe mechanism according to claim 1', wlliereinthe: servometor-c'omiected variable-fulcrum-establismng means comprises ae twin sur'- facci-cam connected for to-and-tro-movement' or'withthe seri/.emptor and' aioll'ower on; the lever engaging bothsurfaces o'f the cam for'p'ositive. movement ofthev lever by the cam in op'- posite directions.

3. The mechanism according to claims 1 and 2 wherein the cam surfaces include dwell portions engaged by the follower when the servomotor has moved to a predetermined position in the fuel-on direction approximately appropriate to full load.

4. The mechanism according to claim 1, wherein the speed measuring device comprises loading-spring-biased lyballs operatingly connected to the valve plunger of the servo-piston by a pushrod which can move away from that plunger without carrying the plunger with it, and the servo piston valve plunger has a return spring connected to move both it and the push rod in a direction opposite that in which the loading spring acts on the nushrod.

5. In a hydraulic relay speed governor for engines, the governor having speed setting means acting through speed-change-responsive pilot valve means to cause engine-fuel-regulating movement of a servomotor, a load limiting valve between the pilot valve and a pressure chamber of the servomotor, which chamber receives fluid under control of the pilot valve to cause fuel-0n movement of the servomotor, the load limiting valve including a plunger slidable in a valve sleeve which sleeve has a port closed by the plunger to block ow of fluid to said chamber and another port opened by the plunger to spill fluid from said chamber, a floating lever connected to said plunger to move it to said port-closing and portopening positions, servomotor-connected means including a variable-fulcrum-establishing means for the lever for enabling such movement of the lever by the servomotor, an engine-speed-measuring means connected for operation by the engine through the governor and having output means connected to another variable fulcrum for the lever for moving the lever in the same plane as it is moved by the servomotor-connected means, whereby load limiting operation on the servomotor by the load limiting Valve is a combined function of servomotor position and engine speed, and adjusting means operable on the load limiting valve sleeve to move it axially relative to its plunger, thereby to enable the servomotor to render the load limiting valve effective and ineffective in predetermined different portions of the total range of movement of the servomotor.

6. I'he mechanism according to claim 5, wherein the load limiting valve sleeve is in screwthreaded relation to its support, and the adjusting means is an angularly movable member connected to the sleeve through constantly meshing gear teeth.

7. In a hydraulic relay speed governor for engines arranged in an upright casing, the governor having speed setting means acting through speedchange-responsive pilot valve means to cause engine-fuel-regulating movement of a servomotor piston in an approximately horizontal direction, a load limiting valve between the pilot valve and a pressure chamber of the servomotor, which chamber receives fluid under control of the pilot valve to cause fuel-on movement of the servomotor, the load limiting valve including a port closing and port opening upright plunger in a mating sleeve, operable to block flow of fluid to said chamber and to spill fluid from said chamber, a generally horizontal floating lever connected to said plunger to move it to said portclosing and port-opening positions, servomotoroperated means including an upright lever continually connected to the servomotor piston, a

cam operatively connected with the upright lever and a cam follower on the oating lever bearing on the cam. an engine-speed-measuring yball mechanism connected for operation by the engine through the governor and having a vertically acting output element constituting another variable fulcrum for the lever and connected therewith, whereby load limiting operation on the servomotor by the load limiting valve is a combined function of servomotor position and engine speed, and means accessible through the top of the upright casing and connected to the load limiting valve sleeve in a manner to enable relative adjustment of the plunger and sleeve axially.

FLGYD H. SWEET.

References Cited in the iile of this patent UNITED STATES PATENTS nar-A 

